SCSI(3) OpenBSD Programmer's Manual SCSI(3)
NAMEscsireq_buff_decode, scsireq_build, scsireq_decode, scsireq_encode,
scsireq_enter, scsireq_new, scsireq_reset, SCSIREQ_ERROR, scsi_open,
scsi_debug, scsi_debug_output - SCSI User library
SYNOPSIS#include <sys/types.h>#include <sys/scsiio.h>#include <scsi.h>intscsireq_buff_decode(u_char *ptr, size_t len, char *fmt, ...);
struct scsireq *scsireq_build(struct scsireq *s, u_long len, caddr_t buf, u_long flags, );
intscsireq_decode(struct scsireq *, char *fmt, ...);
intscsireq_encode(struct scsireq *, char *fmt, ...);
intscsireq_enter(int fid, struct scsireq *s);
struct scsireq *scsireq_new(void);
struct scsireq *scsireq_reset(struct scsireq *);
intSCSIREQ_ERROR(struct scsireq *);
intscsi_open(const char *path, int flags);
voidscsi_debug(FILE *f, int ret, struct scsireq *s);
FILE *scsi_debug_output(char *s);
DESCRIPTION
These functions use the SCIOCCOMMAND ioctl(2) of the SCSI subsystem to
provide user level access to SCSI commands. The programmer must know the
SCSI CDB (Command Descriptor Block) to perform the desired command.
These functions assist in building up the CDB, submitting it to the SCSI
subsystem, and decoding the result.
Look at the scsi(8) command before using the library directly - simple
programs are best implemented as scripts using that facility.
To provide for security, not all devices accept the SCIOCCOMAND ioctl.
It is accepted by the control device for tape drives, partition D for
disk drives, partition C for CD ROM drives, and any "unknown" device.
The "super scsi" ssc(4) device also accepts the ioctl.
Most of the SCSI library functions build up and manipulate the scsireq
structure found in the include file <sys/scsiio.h>:
#define SENSEBUFLEN 48
typedef struct scsireq {
u_long flags; /* info about the request status and type */
u_long timeout;
u_char cmd[16]; /* 12 is actually the max */
u_char cmdlen;
caddr_t databuf; /* address in user space of buffer */
u_long datalen; /* size of user buffer (request) */
u_long datalen_used; /* size of user buffer (used)*/
u_char sense[SENSEBUFLEN]; /* returned sense will be in here */
u_char senselen; /* sensedata request size (MAX of SENSEBUFLEN)*/
u_char senselen_used; /* return value only */
u_char status; /* what the scsi status was from the adapter */
u_char retsts; /* the return status for the command */
int error; /* error bits */
} scsireq_t;
scsireq_new() allocates a new scsireq structure and returns a pointer to
it or NULL if it can't allocate memory.
scsireq_reset() resets the structure to reasonable values and returns the
same pointer passed in to it. It gracefully handles the NULL pointer
passed in to it so that you can unconditionally use scsireq_new.
scsireq_build() builds up a scsireq structure based on the information
provided in the variable argument list. It gracefully handles a NULL
pointer passed to it.
len is the length of the data phase; the data transfer direction is de-
termined by the flags argument.
buf is the data buffer used during the SCSI data phase. If it is NULL it
is allocated via malloc and scsireq->databuf is set to point to the newly
allocated memory.
flags are the flags defined in <sys/scsiio.h>:
/* bit definitions for flags */
#define SCCMD_READ 0x00000001
#define SCCMD_WRITE 0x00000002
#define SCCMD_IOV 0x00000004
#define SCCMD_ESCAPE 0x00000010
#define SCCMD_TARGET 0x00000020
Only two of these flags are supported in this release of the software:
SCCMD_READ indicates a data in phase (a transfer into the user buffer at
scsireg->databuf ), and SCCMD_WRITE indicates a data out phase (a trans-
fer out of the user buffer).
fmt is a CDB format specifier used to build up the SCSI CDB. This text
string is made up of a list of field specifiers. Field specifiers speci-
fy the value for each CDB field (including indicating that the value be
taken from the next argument in the variable argument list), the width of
the field in bits or bytes, and an optional name. White space is ig-
nored, and the pound sign ('#') introduces a comment that ends at the end
of the current line.
The optional name is the first part of a field specifier and is in curly
braces. The text in curly braces in this example are the names:
{PS} v:b1 {Reserved} 0:b1 {Page Code} v:b6 # Mode
This field specifier has two one bit fields and one six bit field. The
second one bit field is the constant value 0 and the first one bit field
and the six bit field are taken from the variable argument list. Multi
byte fields are swapped into the SCSI byte order in the CDB and white
space is ignored.
When the field is a hex value or the letter v, (e.g., 1A or v) then a
single byte value is copied to the next unused byte of the CDB. When the
letter v is used the next integer argument is taken from the variable ar-
gument list and that value used.
A constant hex value followed by a field width specifier or the letter v
followed by a field width specifier (e.g., 3:4, 3:b4, 3:i3, specifies a
field of a given bit or byte width. Either the constant value or (for
the V specifier) the next integer value from the variable argument list
is copied to the next unused bits or bytes of the CDB.
A decimal number or the letter b followed by a decimal number field width
indicates a bit field of that width. The bit fields are packed as tight-
ly as possible beginning with the high bit (so that it reads the same as
the SCSI spec), and a new byte of the CDB is started whenever a byte
fills completely or when an i field is encountered.
A field width specifier consisting of the letter i followed by either 1,
2, 3 or 4 indicates a 1, 2, 3 or 4 byte integral value that must be
swapped into SCSI byte order (MSB first).
For the v field specifier the next integer argument is taken from the
variable argument list and that value is used swapped into SCSI byte or-
der.
scsireq_decode() is used to decode information from the data in phase of
the SCSI transfer.
The decoding is similar to the command specifier processing of
scsireq_build() except that the data is extracted from the data pointed
to by scsireq->databuf. The stdarg list should be pointers to integers
instead of integer values. A seek field type and a suppression modifier
are added. The * suppression modifier (e.g., *i3 or *b4) suppresses as-
signment from the field and can be used to skip over bytes or bits in the
data, without having to copy them to a dummy variable in the arg list.
The seek field type s permits you to skip over data. This seeks to an
absolute position ( s3) or a relative position ( s+3) in the data, based
on whether or not the presence of the '+' sign. The seek value can be
specified as v and the next integer value from the argument list will be
used as the seek value.
scsireq_buff_decode() decodes an arbitrary data buffer using the method
described above in scsireq_decode().
scsireq_encode() encodes the data phase section of the structure. The
encoding is handled identically as the encoding of the CDB structure by
scsireq_build()
scsireq_enter() submits the built up structure for processing using the
SCIOCCOMMAND ioctl.
SCSIREQ_ERROR() is a macro that determines if the result of the SCIOCCOM-
MAND ioctl may have been in error by examining the host adapter return
code, whether sense was sent or not, and so on.
scsi_open() checks environment variables and initializes the library for
consistent library use and then calls the regular open system call.
scsi_debug() prints the results of a scsireq_enter function to the speci-
fied stdio stream.
scsi_debug_output() requests that the results of all transactions be de-
bugged to the supplied file using scsi_debug().
RETURN VALUES
The function scsireq_new() returns a pointer to storage allocated from
malloc, and therefore potentially a NULL.
The functions scsireq_build() and scsireq_reset() return the same pointer
as the one passed in.
The functions scsireq_buff_decode(and) scsireq_decode() return the number
of assignments performed.
scsireq_encode() returns the number of fields processed.
The function scsireq_enter() returns the result of the ioctl call.
SEE ALSO
scsi(4), scsi(8)BUGS
This only works completely for the 1542C. The host adapter code that
sets up the residual amount of data transfer has to be added to each in-
dividual adapter. This library is usable on the other host adapters;
however, the SCSI driver pretends that the proper amount of data is al-
ways transferred. If you have an Adaptec 174x and can hack contact du-
fault@hda.com and you can have the code to calculate residual data for
the 174x series to integrate and test.
HISTORY
Many systems have comparable interfaces to permit a user to construct a
SCSI command in user space.
The data structure is almost identical to the SGI /dev/scsi data struc-
ture. If anyone knows the name of the authors it should go here; Peter
Dufault first read about it in a 1989 Sun Expert magazine.
Peter Dufault implemented a clone of SGI's interface in 386bsd that led
to this library and the related kernel ioctl. If anyone needs that for
compatibility contact dufault@hda.com.
OpenBSD 2.6 November 20, 1994 4